Checking my information: 71 440 steel crank internally balanced? "HEAVY" rods?

[biomedtechguy]

The research I did was a year ago. When I installed the Passon a855 5 speed I replaced my old flywheel with a billet steel flywheel. That meant I had to determine if the motor had an internally or externally balanced crankshaft.
My understanding is that ALL 71 steel crank 440 motors were forged steel crank equipped AND had "heavy" rods, which I don't know if that's the same as "six pack rods" or not. Unfortunately the pad by the distributor has no relevant stampings like "HP" etc....
The flywheel I got works great, no vibration, but I don't remember which one it is and I can't find out today.
The harmonic balancer and the holes (or lack thereof) in the old flywheel led me to the choice I made.
Can anyone help me out by looking at the harmonic balancer on my motor? Thanks.
It has an "eccentric" weighted area shown in the pictures.

 

[moper]

No. Forged cranks with LY rods were internally balanced with neutral balancer. Forged cranks with 6BBL rods were external, using a special balancer. Most passenger car forged cranks were LY rods. Trucks and HD deals might have LY or 6bbl.

 

[khryslerkid]

http://www.440source.com/dampers.htm

 

[biomedtechguy]

http://www.440source.com/dampers.htm

Thanks khryslerkid. So it appears that my 71 440 in my 70 V-Code 6bbl equipped Roadrunner is a 440 forged steel crank motor with 6 pack rods??
Makes me wonder if they just swapped the harmonic balancer and flywheel from the original 70 440 6bbl motor (that I assume got scattered on a track or street at some point) onto the mystery 71 440 that is in it (no determining stampings on the pad by the distributor) ??
The motor seems to run great with no weird vibrations or anything like that....
Things that make you say "hmmm"....
My harmonic balancer:

And the one from 440 source followed by their description:

Shown above is damper #3512017, commonly known as a "six-pack" damper. This damper can be easily identified by a small .210" thousandths thick elliptical weight attached to the center hub. This version was used in '70 and '71 and has the offset pulley bolt pattern.

 

[moparmarks]

Yours is a 6-pack balancer. 70-71 440 hp motors used the "heavy" 6-pack rods.
I've had truck 440 motors thru 1978 with the heavy rods.

 

[biomedtechguy]

Yours is a 6-pack balancer. 70-71 440 hp motors used the "heavy" 6-pack rods.
I've had truck 440 motor thru 1978 with the heavy rods.

So is it possible to install a 6 pack rod harmonic balancer on a 71 440 that does NOT have 6 pack rods and if so, how would that mismatch manifest itself?
Thanks guys...

 

[moparmarks]

Yes. Would probably cause some vibration.

 

[moper]

No - Installing the 6bbl balancer without the heavy rods would create a problem. If it runs well as-is, they may have had the engine re-balanced with the original balancer. Or it still has heavy rods in it. Most anything is possible after this many years.

 

[khryslerkid]

Interesting

 

[moparnation74]

You have the 6 pack balancer and rods....if I was betting in Vegas.......

 

[dvw]

All of the later HP motors were heavy rod. Unless the motor has been apart and assembled incorrectly that is the correct balancer.
Pull the pan and look. Better than installing it in the car and finding out its incorrect.
Doug

 

[biomedtechguy]

All of the later HP motors were heavy rod. Unless the motor has been apart and assembled incorrectly that is the correct balancer.
Pull the pan and look. Better than installing it in the car and finding out its incorrect.
Doug

Thanks for all of the replies.
The best information on at least identifying the harmonic balancer is this

http://www.440source.com/dampers.htm

so special thanks for that khryslerkid and 440 source...
Doug-thanks as always-this is the motor that has been in my Roadrunner since I bought it! After I got the car and checked the date code finding it to be a 1971 440, I went to the distributor pad for clues but found none. No identifying stampings, whatever is there I have looked up/asked about and I haven't found any significance to the letter or 2 that are there. This only came up when I wanted to change my flywheel. I am pretty sure I got the neutral balance flywheel. It would be great (I guess?) if it has 6 pack rods, right?? 6 pack rods = "heavy" rods??

 

[PurpleBeeper]

Just looking at your harmonic balancer, I'd say you have the "big" aka "six pack" rods in your 71 motor. I think it's a good idea to look inside the oil pan....why not? The six pack rods will be just as thick up by the piston as they are near the crankshaft ends (smaller LY rods get skinnier near the piston end).

Now, "assuming" nobody has internally balanced this motor (assuming), then you may have the wrong flywheel....maybe. On my big rod motor, the harmonic balancer, rods, pistons & flywheel all figured into the engine balance. I had my flywheel checked on a balance machine & was told it shook like crazy.....so my engine is externally balanced (including the flywheel).

 

[PurpleBeeper]

Just looking at your harmonic balancer, I'd say you have the "big" aka "six pack" rods in your 71 motor. I think it's a good idea to look inside the oil pan....why not? The six pack rods will be just as thick up by the piston as they are near the crankshaft ends (smaller LY rods get skinnier near the piston end).

Now, "assuming" nobody has internally balanced this motor (assuming), then you may have the wrong flywheel....maybe. On my big rod motor, the harmonic balancer, rods, pistons & flywheel all figured into the engine balance. I had my flywheel checked on a balance machine & was told it shook like crazy.....so my engine is externally balanced (including the flywheel).

harmonic balancer, crank, pistons, rods & flywheel are a "set" on an externally balanced engines. This makes swapping flywheels a pain in the butt. If an engine is internally balanced ("zero balanced"), you just have make sure whatever part you swap is also internally (zero) balanced...piece of cake.

 

[biomedtechguy]

So....Are 6 pack rod equipped motors internally (neutral) balanced from the factory or externally balanced?

 

[mopar 3 B]

Original balance doesn't matter if the balance was changed. What was originall has just become mute.
What is is what matters.

 

[biomedtechguy]

Original balance doesn't matter if the balance was changed. What was originall has just become mute.
What is is what matters.

How are 6 pack rods equipped motors balanced? Internally or Externally?

 

[moparmarks]

Externally.

 

[PurpleBeeper]

So....Are 6 pack rod equipped motors internally (neutral) balanced from the factory or externally balanced?

Yep, like moparmarks said, the big rod motors are externally balanced.....all the parts are a "set"

 

[dvw]

If your motor runs another with the 6 pac balancer then it has the heavy rods. It should also have an externally balanced flywheel. This can be verified with the flywheel removed. Spin it up on a wheel balancer. Externally balanced heavy rod flywheels are availible.
Doug